1,3-1,4-β-D-glucanase, an enzyme often found in ruminal bacteria, cleaves a β-1,4-glucosidic linkage adjacent to β-1,3-linkages in mixed linkage β-glucans, such as lichenan or barley β-glucan, producing cellobiosyltriose and cellotriosyltetraose. It facilitates plant fiber degradation in the rumens of ruminal animals and therefore has been used as a supplement for non-ruminal animals to increase feed conversion efficiency and animal growth-rate. This enzyme has also been used to substitute for or supplement malt enzymes in beer brewing to reduce processing problems caused by β-glucans from cell walls of the starchy seed endosperm, such as reduced extract yield, lowered rates of wort separation and beer filtration, and formation of hazes and gelatinous precipitates in beer. Nonetheless, the use of this enzyme has been limited by its low catalytic activity and thermal instability. Thus, there is a need for 1,3-1,4-β-D-glucanase that is both highly active and heat resistant.